A Basic Guide to Making a Hollow Concrete Block Mould
Understanding "how to make a hollow concrete block mould" is valuable whether you plan to build a small prototype or need to communicate better with professional manufacturers. Below is a simplified overview of the industrial process used by companies like UNIK.
Step 1: Design the Mould Cavity
Start with the desired block dimensions. A common hollow block size is 390mm x 190mm x 190mm. The two or three hollow cores reduce weight and improve insulation.
Key design elements:
Draft angle (usually 1–3 degrees) to allow the hardened block to release easily
Core design (shape and position of the hollow areas)
Wall thickness between the outer surface and the cores
Step 2: Select the Right Steel
For concrete moulds, the steel must resist abrasion from aggregates (sand, gravel) and repeated impacts from vibration. Quality manufacturers use high-carbon alloy steel or tool steel such as Cr12MoV or 42CrMo. For very high-volume production, imported steel like Creusabro is preferred.
Step 3: Machine the Mould Cavities
Using CNC milling machines or electrical discharge machining (EDM), the cavity shape including cores is cut into solid steel blocks. This step requires high precision. Deviations of even 0.1mm can affect block dimensions and demoulding.
Step 4: Heat Treatment
After machining, the mould is heat-treated to increase surface hardness (typically 55–62 HRC). This is the most critical step for mould longevity. The mould must be hard enough to resist wear but tough enough not to crack under vibration.
Step 5: Grinding and Finishing
The cavity surfaces are ground and polished to a smooth finish. A smoother surface makes demoulding easier and improves the surface quality of the concrete block.
Step 6: Assemble the Mould Frame
The mould cavity is mounted into a sturdy steel frame designed to fit your specific block making machine (e.g., a stationary or mobile machine). The frame holds everything rigid during the vibration and compaction process.